The Evidence
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A classic example of biochemical evidence for evolution is the variance of the proteinCytochrome c in living cells. The variance of cytochrome c of different organisms is measured in the number of differing amino acids, each differing amino acid being a result of a base pair substitution, a mutation. If each differing amino acid is assumed to be the result of one base pair substitution, it can be calculated how long ago the two species diverged by multiplying the number of base pair substitutions by the estimated time it takes for a substituted base pair of the cytochrome c gene to be successfully passed on.
Due to mutations, the sequence of nucleotides in a gene gradually changes over time. The more closely related two organisms are, the less different their DNA will be. Genes evolve at different rates because, although mutation is a random event, some proteins are much more tolerant of changes in their amino acid sequence than are other proteins.The average rate at which a particular kind of gene or protein evolves gives rise to the concept of a "molecular clock." It determines evolutionary relationships among organisms, and it indicates the time in the past when species started to diverge from one another. Once the clock for a particular gene or protein has been calibrated by reference to some event whose time is known, the actual chronological time when all other events occurred can be determined by examining the protein or gene tree.
"The researchers studied the Hox genes, which help cells organize into different body parts during development. Three disparate animals were studied: an unsegmented marine worm, a lamp shell, and a segmented worm. Based on the traditional animal family tree, these organisms are seemingly unrelated.
The findings were astounding! Looking at the genes, scientists found support for the three-limb theory. The Hox genes in each of the animals studied were very similar but with small (and significant) differences. Those differences point to a common ancestor that eventually diverged into the three different paths. The genetic analysis suggests that these three branches diverged some 550 million years ago from a common ancestor."
Fairly recent studies show that scientists have found that in every multicelled organism, there are two three-dimensional proteins. These two proteins are called hemoglobin and myoglobin. Myoglobin consists of 153 amino acids, wrapped in a structure called “heme”. Hemoglobin, unlike myoglobin, consists of four chains, two with 141 amino acids and 2 with 146 amino acids. The interesting fact about these chains however, is that each is also in the structure of a heme, showing the hemoglobin and myoglobin are somewhat closely related.
Molecular Biology is the study of molecular basis of l ife processes which include cellular respiration, excretion, and reproduction. In 1938, the term "Molecular Biology" was coined by Warren Weaver, who was the director of the natural sciences program at the Rockefeller Foundation. In 1950 W. T. Astbury of the Univ. of Leeds used the term in its now accepted sense, to describe the area of research, closely related to and often overlapping biochemistry, conducted by biologists whose approach to and interest in biology are principally at the molecular level of organization. Thanks to ultracentrifugation in the 1930's, macromolecules were first studied in detail and their crystalline prperties described. In the 1940's scientists found base pairs and in the 50's, Pauling described the 3D structure of proteins and Watson and Crick created the double helix structure.
Molecular Biology is dependant on other things besides biology, such as chemistry and genetics. In order to understand the interactions between DNA, RNA, proteins and lipids, its important to understand how cells work and how different diseases affcet these interactions. Researchers are slowly putting together these interactions and therefore starting to better understand how each biological molecule works. Once scientists fully understand it will be easier to examine different disease conditions. This in the long run will help them to be able to repair and cure diseases. Molecular Biology is a vital aspect in the advancement of medicine. By being able to understand how cells work and function Biolgoists will be better and equipped to detect and fix disease earlier.
"Pseudogenes" is another piece of evidence supporting evolution through molecular biology. Pseudogenes are sequences of DNA that are remnants of genes no longer able to function. However, they are continually passed down through DNA as "excess baggage." Pseudogenes also change through time, as they are passed on from ancestors to descendants, and they offer an especially useful way of reconstructing evolutionary relationships. Thus, the degree of similarity between any two organisms' pseudogenes must reflect their "evolutionary relatedness." The more similar the last common ancestor of the two organisms, the more alike their pseudogenes will be.
Evidence for evolution from Molecular Biology can help us go beyond paleontological evidence. For an example, for a long while we have thought that whales are land mammals that reverted to sea life. "From anatomical and palentological evidence, the whales' closest living land relatives seemed to be the even-toed hoofed mammals (modern cattle, sheep...etc). Recent comparisons of some milk protein genes (beta-casein and kappa-casein) have confirmed this relationship and have suggested that the closest land-bound living relative of whales may be the hippopotamus. In this case, molecular biology has augmented the fossil record."
Describe a piece of evidence you found
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The findings were astounding! Looking at the genes, scientists found support for the three-limb theory. The Hox genes in each of the animals studied were very similar but with small (and significant) differences. Those differences point to a common ancestor that eventually diverged into the three different paths. The genetic analysis suggests that these three branches diverged some 550 million years ago from a common ancestor."